# CVE-2025-34127: Achat v0.150 SEH Buffer Overflow via UDP

> Remote attackers can execute arbitrary code on Achat Chat Server by sending crafted UDP packets to trigger a stack-based buffer overflow.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Jul 2025
- **Updated:** 7 Apr 2026
- **Also known as:** GHSA-pfrw-7rxm-j92h

## What is CVE-2025-34127?

CVE-2025-34127 is a critical memory corruption vulnerability in Achat Chat Server, published on 16 Jul 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A stack-based buffer overflow exists in Achat v0.150 in its default configuration. By sending a specially crafted message to the UDP port 9256, an attacker can overwrite the structured exception handler (SEH) due to insufficient bounds checking on user-supplied input leading to remote code execution.

Weakness: CWE-94 (Improper Control of Generation of Code), CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2025-34127?


## How do I fix CVE-2025-34127?

No fix has been published for CVE-2025-34127 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-34127 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-34127 exists.

Public exploit code:

- Achat Unicode SEH Buffer Overflow (metasploit)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-34127 and fix it if it is affected.

What it is: CVE-2025-34127 is a critical memory corruption vulnerability in Achat Chat Server, published on 16 Jul 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-34127 exists.

Affected product: Achat Chat Server. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-34127/ (Markdown: https://insights.sbomify.com/CVE-2025-34127/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-34127
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-34127
- OSV: https://osv.dev/vulnerability/CVE-2025-34127

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-34127/
Summaries are generated and may contain mistakes; the official description above is the record.